Non-planar i/o and logic semiconductor devices having different workfunction on common substrate

ABSTRACT

Non-planar I/O and logic semiconductor devices having different workfunctions on common substrates and methods of fabricating non-planar I/O and logic semiconductor devices having different workfunctions on common substrates are described. For example, a semiconductor structure includes a first semiconductor device disposed above a substrate. The first semiconductor device has a conductivity type and includes a gate electrode having a first workfunction. The semiconductor structure also includes a second semiconductor device disposed above the substrate. The second semiconductor device has the conductivity type and includes a gate electrode having a second, different, workfunction.

CLAIM OF PRIORITY

This application is a continuation of U.S. patent application Ser. No.14/914,179 filed Feb. 24, 2016, which is a U.S. National Phaseapplication under 35 U.S.C. § 371 of International Application No.PCT/US2013/062308, filed Sep. 27, 2013, entitled “NON-PLANAR I/O ANDLOGIC SEMICONDUCTOR DEVICES HAVING DIFFERENT WORKFUNCTION ON COMMONSUBSTRATE” the entire contents of which are incorporated herein byreference.

TECHNICAL FIELD

Embodiments of the invention are in the field of semiconductor devicesand processing and, in particular, non-planar I/O and logicsemiconductor devices having different workfunctions on commonsubstrates and methods of fabricating non-planar I/O and logicsemiconductor devices having different workfunctions on commonsubstrates.

BACKGROUND

For the past several decades, the scaling of features in integratedcircuits has been a driving force behind an ever-growing semiconductorindustry. Scaling to smaller and smaller features enables increaseddensities of functional units on the limited real estate ofsemiconductor chips. For example, shrinking transistor size allows forthe incorporation of an increased number of memory or logic devices on achip, lending to the fabrication of products with increased capacity.The drive for ever-more capacity, however, is not without issue. Thenecessity to optimize the performance of each device becomesincreasingly significant.

In the manufacture of integrated circuit devices, multi-gatetransistors, such as fin field effect transistors (fin-FETs), havebecome more prevalent as device dimensions continue to scale down. Inconventional processes, fin-FETs are generally fabricated on either bulksilicon substrates or silicon-on-insulator substrates. In someinstances, bulk silicon substrates are preferred due to their lower costand compatibility with the existing high-yielding bulk silicon substrateinfrastructure.

Scaling multi-gate transistors has not been without consequence,however. As the dimensions of these fundamental building blocks ofmicroelectronic circuitry are reduced and as the sheer number offundamental building blocks fabricated in a given region is increased,the constraints on the semiconductor processes used to fabricate thesebuilding blocks have become overwhelming.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A illustrates a cross-sectional view of an incomplete portion of asemiconductor structure having an I/O transistor and a logic transistordisposed on a common substrate.

FIG. 1B illustrates a cross-sectional view of an incomplete portion of asemiconductor structure having an I/O transistor and a logic transistordisposed on a common substrate, in accordance with an embodiment of thepresent invention.

FIGS. 2A-2F illustrate cross-sectional view of various operations in amethod of fabricating an I/O transistor and a logic transistor on acommon substrate, in accordance with an embodiment of the presentinvention, where:

FIG. 2A illustrates an incomplete semiconductor structure having ahardmask form in gate electrode regions of a logic transistor, but notin gate electrode regions of an I/O transistor;

FIG. 2B illustrates the structure of FIG. 2A having the portion of theworkfunction metal layer at gate electrode regions of the I/O transistorremoved;

FIG. 2C illustrates the structure of FIG. 2B having a secondworkfunction metal layer and a second hardmask layer formed thereon;

FIG. 2D illustrates the structure of FIG. 2C following recessing of thesecond hardmask layer;

FIG. 2E illustrates the structure of FIG. 2D following removal ofexposed portions of the second workfunction layer; and

FIG. 2F illustrates the structure of FIG. 2E following removal ofremaining portions of the hardmask layer and second hardmask layer.

FIG. 3A illustrates a cross-sectional view of a non-planar semiconductordevice, in accordance with an embodiment of the present invention.

FIG. 3B illustrates a plan view taken along the a-a′ axis of thesemiconductor device of FIG. 3A, in accordance with an embodiment of thepresent invention.

FIG. 4 illustrates a computing device in accordance with oneimplementation of the invention.

DESCRIPTION OF THE EMBODIMENTS

Non-planar I/O and logic semiconductor devices having differentworkfunctions on common substrates and methods of fabricating non-planarI/O and logic semiconductor devices having different workfunctions oncommon substrates are described. In the following description, numerousspecific details are set forth, such as specific integration andmaterial regimes, in order to provide a thorough understanding ofembodiments of the present invention. It will be apparent to one skilledin the art that embodiments of the present invention may be practicedwithout these specific details. In other instances, well-known features,such as integrated circuit design layouts, are not described in detailin order to not unnecessarily obscure embodiments of the presentinvention. Furthermore, it is to be understood that the variousembodiments shown in the Figures are illustrative representations andare not necessarily drawn to scale.

One or more embodiments described herein are directed to approaches toof fabricating multiple workfunctions (WF) for different pitches ofsemiconductor devices fabricated on a common substrate. Applications maybe in the fabrication of metal oxide semiconductor (MOS) and structureshaving both I/O transistors (e.g., drive transistor) and logictransistors (e.g., computation transistors) fabricated from a sharedprocess scheme on a common substrate. In an example, the I/O transistorsare fabricated to have a larger gate length and different workfunctionas compared to the corresponding logic transistors.

To provide context, presently, the performances of different devices insystem on chip (SoC) integrated circuits are controlled by differentpitch, critical dimension (CD) and implant tailoring. However, alldevices of a same conductivity type (e.g., N-type of P-type) typicallyhave a same work function (WF). By contrast, one or more embodimentsdescribed herein provides an approach to patterning different workfunctions for different devices, enabling independent controlperformance of each device type.

More specifically, one or more embodiments take advantage of an etchrate dependence of a carbon hard mask (CHM) between different structureswith different CDs (e.g., a wider CD has faster etch rate than anarrower CD). As such, different workfunction layers (such as metal gatelayers) can be patterned for different devices (e.g., I/O versus logicdevices). One or more embodiments, then, provide an opportunity toachieve different actual gate workfunctions for like devices (e.g.,N-type devices) having differing function, e.g., an I/O device versus alogic device. By differentiating the workfunction between devices, theperformance of each device can be independently targeted without use ofany additional mask operations.

Previous approaches for providing different effective gate workfunctionsfor like devices (e.g., N-type devices) having differing function, e.g.,an I/O device versus a logic device, have involved the use of substrateimplant differentiation to control the performance of different devices.As an example, FIG. 1A illustrates a cross-sectional view of anincomplete portion of a semiconductor structure 100A having an I/Otransistor 102A and a logic transistor 104A disposed on a commonsubstrate 101A and separated by an inter-layer dielectric region 103A.Referring to FIG. 1A, the I/O transistor 102A is formed over a first fin106A, and the logic transistor 104A is formed over a second fin 108A. Inthe particular example shown, the I/O transistor 102A has threerelatively wider gate electrode regions 110A, 112A and 114A(cross-sectional view shows the gate length 111A as taken betweensource/drain regions). The underlying fin 106A can include epitaxialsource/drain regions 116A, as shown. Meanwhile, the logic transistor104A has three relatively narrower gate electrode regions 120A, 122A and124A (cross-sectional view shows the gate length 121A as taken betweensource/drain regions). The underlying fin 108A can also includeepitaxial source/drain regions 126A, as shown.

Referring again to FIG. 1A, at the point of processing depicted, areplacement gate process has been performed where a dummy gate materialis replaced with a workfunction metal layer 118A at gate electroderegions 110A, 112A, 114A, 120A, 122A and 124A. However, the workfunctionmetal layer 118A is the same for the gate electrode regions of both theI/O transistor 102A and the logic transistor 104A. Therefore, in orderto differentiate the effective workfunction of the I/O transistor 102Aand the logic transistor 104A, approaches such as fin dopingdifferentiation are used. It is to be understood that additionalprocessing can subsequently be performed to complete the devices of FIG.1A, such as gate fill, contact formation, and back-end of line (BEOL)interconnect fabrication.

In contrast to the arrangement described in association with FIG. 1A,FIG. 1B illustrates a cross-sectional view of an incomplete portion of asemiconductor structure 100B having an I/O transistor 102B and a logictransistor 104B disposed on a common substrate 101B and separated by aninter-layer dielectric region 103B, in accordance with an embodiment ofthe present invention. Referring to FIG. 1B, the I/O transistor 102B isformed over a first fin 106B, and the logic transistor 104B is formedover a second fin 108B. In the particular example shown, the I/Otransistor 102B has three relatively wider gate electrode regions 110B,112B and 114B (cross-sectional view shows the gate length 111B as takenbetween source/drain regions). The underlying fin 106B can includeepitaxial source/drain regions 116B, as shown. Meanwhile, the logictransistor 104B has three relatively narrower gate electrode regions120B, 122B and 124B (cross-sectional view shows the gate length 121B astaken between source/drain regions). The underlying fin 108B can alsoinclude epitaxial source/drain regions 126B, as shown.

Referring again to FIG. 1B, at the point of processing depicted, areplacement gate process has been performed where a dummy gate materialis replaced with a workfunction metal layer 118B at gate electroderegions 120B, 122B and 124B of the logic transistor 104B. However, in anembodiment, the gate electrode regions 110B, 112B and 114B of the I/Otransistor 102B includes a different workfunction metal layer 119, evenfor the same conductivity-type device (i.e., in the case where both theI/O transistor 102B and the logic transistor 104B are N-type, or boththe I/O transistor 102B and the logic transistor 104B are P-type). In anembodiment, the workfunction metal layer 119 has an actual workfunctiondifferent than the actual workfunction of the workfunction metal layer118B. In one such embodiment, the workfunction metal layer 119 hasthickness different than the thickness of the workfunction metal layer118B (as shown). In another such embodiment, the workfunction metallayer 119 has a total material composition different than the totalmaterial composition of the workfunction metal layer 118B. In yetanother embodiment, the workfunction metal layer 119 differs from theworkfunction metal layer 118B in both thickness and total materialcomposition. In a particular embodiment, the I/O transistor 102B and thelogic transistor 104B are both N-type devices, and the workfunctionmetal layer 119 is composed of substantially the same material as theworkfunction metal layer 118B but is thicker than the workfunction metallayer 118B; the actual workfunction of the workfunction metal layer 119,as compared with the actual workfunction of the workfunction metal layer118B, is shifted towards mid-gap from N-type by an amount approximatelyin the range of 50-80 mVolts. It is to be understood that additionalprocessing can subsequently be performed to complete the devices of FIG.1B, such as gate fill, contact formation, and back-end of line (BEOL)interconnect fabrication. It is also to be understood that, although notdepicted, a gate dielectric layer can be disposed between theworkfunction metal layers 118B and 119 and the fins 108B and 106B,respectively.

In an aspect, a semiconductor fabrication scheme can involve fabricationof different workfunction layers for functionally different devices oflike conductivity type. As an example, FIGS. 2A-2F illustratecross-sectional view of various operations in a method of fabricating anI/O transistor and a logic transistor on a common substrate, inaccordance with an embodiment of the present invention.

Referring to FIG. 2A, an incomplete portion 200 of a semiconductorstructure includes an I/O transistor 202 and a logic transistor 204disposed on a common substrate 201. The I/O transistor 202 is formedover a first fin 206, and the logic transistor 204 is formed over asecond fin 208. In the particular example shown, the I/O transistor 202has three relatively wider gate electrode regions 210, 212 and 214(cross-sectional view shows the gate length 211 as taken betweensource/drain regions). The underlying fin 206 can include epitaxialsource/drain regions 216, as shown. Meanwhile, the logic transistor 204has three relatively narrower gate electrode regions 220, 222 and 224(cross-sectional view shows the gate length 221 as taken betweensource/drain regions). The underlying fin 208 can also include epitaxialsource/drain regions 226, as is also shown.

Referring again to FIG. 2A, at the point of processing depicted, areplacement gate process has been performed where a dummy gate materialis replaced with a workfunction metal layer 218 at gate electroderegions 210, 212, 214, 220, 222 and 224. It is to be understood that, atthis stage, the actual workfunction of the workfunction metal layer 218is the same for the gate electrode regions of both the I/O transistor202 and the logic transistor 204. In particular, the workfunction metallayer 218 is formed at the same time, and in the same process operation,for both the I/O transistor 202 and the logic transistor 204. It is alsoto be understood that, although not depicted, a gate dielectric layercan be disposed between the workfunction metal layer 218 and the fins208 and 206B. Also shown in FIG. 2A are gate electrode spacers 228 andinterlayer dielectric regions 229.

Referring again to FIG. 2A, a hardmask layer 230 is formed on portionsof the incomplete semiconductor structure 200. In particular thehardmask layer 230 is formed between the I/O transistor 202 and thelogic transistor 204 and, most importantly, within the gate electrodelocations 220, 222 and 224 of the logic transistor 204. The hardmasklayer 230 is however, not formed in (or is removed from) the gateelectrode locations 210, 212 and 214 of the I/O transistor 202, as isdepicted. In accordance with an embodiment of the present invention, thehardmask layer is first formed globally, i.e., the hardmask layer 230 isfirst formed between the I/O transistor 202 and the logic transistor204, within the gate electrode locations 220, 222 and 224 of the logictransistor 204, and within the gate electrode locations 210, 212 and 214of the I/O transistor 202. The portions of the hardmask layer 230 withinthe gate electrode locations 210, 212 and 214 of the I/O transistor 202is then removed. In one such embodiment, the hardmask layer 230 is firstformed globally by a spin-on process. The spin-on layer is then etchedselective to other present materials and features to reduce the heightof the layer. In an example, the etch rates at different featurelocations can vary. As such, in one embodiment, the hardmask layeretches faster from the wider features 210, 212 and 214 than from therelatively narrower features 220, 222, and 224. Accordingly, the spin-onlayer may be removed entirely from the wider features 210, 212 and 214,while a portion of the spin-on layer is retained in narrower features220, 222, and 224, as depicted. It is to be understood that the portionof the spin-on layer between devices 202 and 204 may be removed ratherthan retained in the etch process. In an embodiment, the hardmask layer230 is composed substantially of carbon and is referred to as a carbonhardmask (CHM) layer.

Referring to FIG. 2B, the portion of the workfunction metal layer 218 atgate electrode regions 210, 212 and 214 (i.e., at the I/O transistor202) is removed. In an embodiment, the portion of the workfunction metallayer 218 at gate electrode regions 210, 212 and 214 is removedselective to the hardmask layer 230. In one such embodiment, at thelogic transistor 204, upper portions of the workfunction metal layer 218not protected by the hardmask layer 230 are also removed, as isdepicted. Furthermore, if a gate dielectric layer is present on fin 206,it may be removed at this time, or it may be preserved. In anembodiment, the exposed portions of the workfunction metal layer 218 areremoved by a selective etch process such as a wet etch process, dry etchprocess, or a combination thereof.

Referring to FIG. 2C, a second workfunction metal layer 240 is formed onthe structure of FIG. 2B. More particularly, the second workfunctionmetal layer 240 is formed in the gate electrode locations 210, 212 and214 of the I/O transistor 202. Additionally, the second workfunctionmetal layer 240 can be formed on the exposed portions of theworkfunction metal layer 218 and the hardmask layer 230 remaining in thegate electrode locations 220, 222 and 224 of the logic transistor, as isdepicted in FIG. 2C. In an embodiment, the second workfunction metallayer 240 has an actual workfunction different than the actualworkfunction of the workfunction metal layer 218. In one suchembodiment, the second workfunction metal layer 240 has thicknessdifferent than the thickness of the workfunction metal layer 218 (asshown). In another such embodiment, the second workfunction metal layer240 has a total material composition different than the total materialcomposition of the workfunction metal layer 218. In yet anotherembodiment, the second workfunction metal layer 240 differs from theworkfunction metal layer 218 in both thickness and total materialcomposition. In a particular embodiment, the I/O transistor 202 and thelogic transistor 204 are both N-type devices, and the secondworkfunction metal layer 240 is composed of substantially the samematerial as the workfunction metal layer 218 but is thicker than theworkfunction metal layer 218; the actual workfunction of the secondworkfunction metal layer 240, as compared with the actual workfunctionof the workfunction metal layer 218, is shifted towards mid-gap fromN-type by an amount approximately in the range of 50-80 mVolts.

It is to be understood that, in the case that a gate dielectric layerwas removed from the I/O transistor of FIG. 2B, a gate dielectric layermay be formed immediately prior to the formation of the secondworkfunction metal layer 240. Referring again to FIG. 2C, a secondhardmask layer 242 is then formed above the second workfunction metallayer 240. In one such embodiment, the second hardmask layer 242 iscomposed of the same material or substantially the same material ashardmask layer 230. For example, in one such embodiment, the secondhardmask layer 242 is a carbon hardmask layer.

Referring to FIG. 2D, the second hardmask layer 242 is etched to recessthe portions in the gate electrode regions 210, 212 and 214 of the I/Otransistor 202. In the case of the logic transistor 204, the etchingremoves the second hardmask layer 242 from the gate electrode regions220, 222 and 224 of the logic transistor 204. Furthermore, the recessingof the second hardmask layer 242 exposes portions of the secondworkfunction metal layer 240 at both the I/O transistor 202 and thelogic transistor 204. In an embodiment, the second hardmask layer 242 isrecessed by a selective etch process such as an ash process, wet etchprocess, dry etch process, or a combination thereof.

Referring to FIG. 2E, portions of the second workfunction metal layer240 exposed upon recessing the second hardmask layer 242 are removedfrom both the I/O transistor 202 and the logic transistor 204. In anembodiment, the exposed portions of the second workfunction metal layer242 are removed by a selective etch process such as a wet etch process,dry etch process, or a combination thereof.

Referring to FIG. 2F, remaining portions of the hardmask layer 230 andthe second hardmask layer 242 are removed. The removal exposes theformed and patterned second workfunction metal layer 240 in the gateelectrode regions 210, 212, and 214 of the I/O transistor 202 and alsoexposes the formed and patterned workfunction metal layer 218 in thegate electrode regions 220, 222 and 224 of the logic transistor 204. Inan embodiment, the remaining portions of the hardmask layer 230 and thesecond hardmask layer 242 are removed by a selective etch process suchas an ash process, wet etch process, dry etch process, or a combinationthereof. Referring again to FIG. 2F, a dielectric region 230′ is shownbetween the transistors. Although the region 230′ may be a region ofpreserved hardmask, this regions may also be removed and subsequentlyreplaced with an inter-layer dielectric material. It is also to beunderstood that additional processing can subsequently be performed tocomplete the devices of FIG. 2F, such as gate fill, contact formation,and back-end of line (BEOL) interconnect fabrication.

In general, referring again to FIGS. 2A-2F, in an embodiment, theapproach described can be used for N-type (e.g., NMOS) or P-type (e.g.,PMOS), or both, device fabrication. It is to be understood that thestructures resulting from the above exemplary processing scheme, e.g.,the structures from FIG. 2F, may be used in a same or similar form forsubsequent processing operations to complete device fabrication, such asPMOS and NMOS device fabrication. As an example of a completed device,FIGS. 3A and 3B illustrate a cross-sectional view and a plan view (takenalong the a-a′ axis of the cross-sectional view), respectively, of anon-planar semiconductor device such as completed versions of the I/Odevice 202 or the logic device 204, in accordance with an embodiment ofthe present invention. It is to be noted that the cross-sectional viewof FIG. 3A is taken orthogonal to the cross-sectional view of FIG. 2F,as taken along any one of the gate lines 210, 212, 214, 220, 222 or 224.Furthermore, in the example, illustrated in FIGS. 3A and 3B, the gatelines cover three distinct semiconductor fins.

Referring to FIG. 3A, a semiconductor structure or device 300, such ascompleted versions of the I/O transistor 202 or the logic transistor204, includes a non-planar active region (e.g., a fin structureincluding a protruding fin portion 304 and a sub-fin region 305) formedfrom a substrate 302, and within an isolation region 306.

Referring again to FIG. 3A, a gate line 308 is disposed over theprotruding portions 304 of the non-planar active region as well as overa portion of the isolation region 306. As shown, gate line 308 includesa gate electrode 350 and a gate dielectric layer 352. In one embodiment,gate line 308 may also include a dielectric cap layer 354. A gatecontact 314, and overlying gate contact via 316 are also seen from thisperspective, along with an overlying metal interconnect 360, all ofwhich are disposed in inter-layer dielectric stacks or layers 370. Alsoseen from the perspective of FIG. 3A, the gate contact 314 is, in oneembodiment, disposed over isolation region 306, but not over thenon-planar active regions. As shown, the fins 304 are considered to bebulk fins since they extend from the underlying substrate 302. In otherembodiments, the fins are formed from a silicon-on insulator (SOI) typesubstrate and are thus disposed on a global insulator layer.

Referring to FIG. 3B, the gate line 308 is shown as disposed over theprotruding fin portions 304. Source and drain regions 304A and 304B ofthe protruding fin portions 304 can be seen from this perspective. Inone embodiment, the source and drain regions 304A and 304B are dopedportions of original material of the protruding fin portions 304. Inanother embodiment, the material of the protruding fin portions 304 isremoved and replaced with another semiconductor material, e.g., byepitaxial deposition. In either case, the source and drain regions 304Aand 304B may extend below the height of dielectric layer 306, i.e., intothe sub-fin region 305, in the case of bulk type devices. Alternatively,the source and drain regions 304A and 304B do not extend below theheight of dielectric layer 306, and are either above or co-planar withthe height of dielectric layer 306.

In an embodiment, the semiconductor structure or device 300 is anon-planar device such as, but not limited to, a fin-FET or a tri-gateor similar device. In such an embodiment, a corresponding semiconductingchannel region is composed of or is formed in a three-dimensional body.In one such embodiment, the gate electrode stacks of gate lines 308surround at least a top surface and a pair of sidewalls of thethree-dimensional body, as depicted in FIG. 3A.

Substrates 201 and 302 described in association with FIGS. 2A-2F and 3A,respectively, may be composed of a semiconductor material that canwithstand a manufacturing process and in which charge can migrate. In anembodiment, substrate 201 or 302 is a bulk substrate composed of acrystalline silicon, silicon/germanium or germanium layer doped with acharge carrier, such as but not limited to phosphorus, arsenic, boron ora combination thereof. In one embodiment, the concentration of siliconatoms in bulk substrate 201 or 302 is greater than 97%. In anotherembodiment, bulk substrate 201 or 302 is composed of an epitaxial layergrown atop a distinct crystalline substrate, e.g. a silicon epitaxiallayer grown atop a boron-doped bulk silicon mono-crystalline substrate.Bulk substrate 201 or 302 may alternatively be composed of a group III-Vmaterial. In an embodiment, bulk substrate 201 or 302 is composed of aIII-V material such as, but not limited to, gallium nitride, galliumphosphide, gallium arsenide, indium phosphide, indium antimonide, indiumgallium arsenide, aluminum gallium arsenide, indium gallium phosphide,or a combination thereof. In one embodiment, bulk substrate 201 or 302is composed of a III-V material and the charge-carrier dopant impurityatoms are ones such as, but not limited to, carbon, silicon, germanium,oxygen, sulfur, selenium or tellurium. Alternatively, in place of a bulksubstrate, a silicon-on-insulator (SOI) substrate may be used. In such acase, the region 201 depicted in FIGS. 2A-2F is a global isolationlayer.

Isolation region 306 may be composed of a material suitable toultimately electrically isolate, or contribute to the isolation of,portions of a permanent gate structure from an underlying bulk substrateor isolate active regions formed within an underlying bulk substrate,such as isolating fin active regions. For example, in one embodiment,the isolation region 306 is composed of a dielectric material such as,but not limited to, silicon dioxide, silicon oxy-nitride, siliconnitride, or carbon-doped silicon nitride.

Gate line 308 may be composed of a gate electrode stack which includes agate dielectric layer 352 and a gate electrode layer 350 (such asworkfunction metal layer 218 or 240). In an embodiment, the gateelectrode of the gate electrode stack is composed of a metal gate andthe gate dielectric layer is composed of a high-K material. For example,in one embodiment, the gate dielectric layer is composed of a materialsuch as, but not limited to, hafnium oxide, hafnium oxy-nitride, hafniumsilicate, lanthanum oxide, zirconium oxide, zirconium silicate, tantalumoxide, barium strontium titanate, barium titanate, strontium titanate,yttrium oxide, aluminum oxide, lead scandium tantalum oxide, lead zincniobate, or a combination thereof. Furthermore, a portion of gatedielectric layer may include a layer of native oxide formed from the topfew layers of the substrate 302. In an embodiment, the gate dielectriclayer is composed of a top high-k portion and a lower portion composedof an oxide of a semiconductor material. In one embodiment, the gatedielectric layer is composed of a top portion of hafnium oxide and abottom portion of silicon dioxide or silicon oxy-nitride.

In one embodiment, the gate electrode layer 350 (such as workfunctionmetal layer 218 or 240) is composed of a metal layer such as, but notlimited to, metal nitrides, metal carbides, metal silicides, metalaluminides, hafnium, zirconium, titanium, tantalum, aluminum, ruthenium,palladium, platinum, cobalt, nickel or conductive metal oxides. In aspecific embodiment, the gate electrode is composed of anon-workfunction-setting fill material formed above a metalworkfunction-setting layer.

Spacers associated with the gate electrode stacks (shown as 228 in FIGS.2A-2F) may be composed of a material suitable to ultimately electricallyisolate, or contribute to the isolation of, a permanent gate structurefrom adjacent conductive contacts, such as self-aligned contacts. Forexample, in one embodiment, the spacers are composed of a dielectricmaterial such as, but not limited to, silicon dioxide, siliconoxy-nitride, silicon nitride, or carbon-doped silicon nitride.

Gate contact 314 and overlying gate contact via 316 may be composed of aconductive material. In an embodiment, one or more of the contacts orvias are composed of a metal species. The metal species may be a puremetal, such as tungsten, nickel, or cobalt, or may be an alloy such as ametal-metal alloy or a metal-semiconductor alloy (e.g., such as asilicide material).

In an embodiment, the gate line 308 (or lines 210, 212, 214, 220, 222and 224) are first formed by poly gate patterning involving polylithography to define the poly gate by etch of an SiN hardmask and polysubsequently. In one embodiment, a mask is formed on the hardmask layer,the mask composed of a topographic masking portion and ananti-reflective coating (ARC) layer. In a particular such embodiment,the topographic masking portion is a carbon hardmask (CHM) layer and theanti-reflective coating layer is a silicon ARC layer. The topographicmasking portion and the ARC layer may be patterned with conventionallithography and etching process techniques. In one embodiment, the maskalso includes and uppermost photo-resist layer, as is known in the art,and may be patterned by conventional lithography and developmentprocesses. In a particular embodiment, the portions of the photo-resistlayer exposed to the light source are removed upon developing thephoto-resist layer. Thus, patterned photo-resist layer is composed of apositive photo-resist material. In a specific embodiment, thephoto-resist layer is composed of a positive photo-resist material suchas, but not limited to, a 248 nm resist, a 193 nm resist, a 157 nmresist, an extreme ultra violet (EUV) resist, an e-beam imprint layer,or a phenolic resin matrix with a diazonaphthoquinone sensitizer. Inanother particular embodiment, the portions of the photo-resist layerexposed to the light source are retained upon developing thephoto-resist layer. Thus, the photo-resist layer is composed of anegative photo-resist material. In a specific embodiment, thephoto-resist layer is composed of a negative photo-resist material suchas, but not limited to, consisting of poly-cis-isoprene orpoly-vinyl-cinnamate.

Furthermore, as mentioned briefly in association with FIG. 2A, the gatestack structure 308 (and gates electrode locations 210, 212, 214, 220,222 and 224) may be fabricated by a replacement gate process. In such ascheme, dummy gate material such as polysilicon or silicon nitridepillar material, may be removed and replaced with permanent gateelectrode material. In one such embodiment, a permanent gate dielectriclayer is also formed in this process, as opposed to being carriedthrough from earlier processing. In an embodiment, dummy gates areremoved by a dry etch or wet etch process. In one embodiment, dummygates are composed of polycrystalline silicon or amorphous silicon andare removed with a dry etch process including use of SF₆. In anotherembodiment, dummy gates are composed of polycrystalline silicon oramorphous silicon and are removed with a wet etch process including useof aqueous NH₄OH or tetramethylammonium hydroxide. In one embodiment,dummy gates are composed of silicon nitride and are removed with a wetetch including aqueous phosphoric acid.

In an embodiment, one or more approaches described herein contemplateessentially a dummy and replacement gate process in combination with adummy and replacement contact process. In one such embodiment, thereplacement contact process is performed after the replacement gateprocess to allow high temperature anneal of at least a portion of thepermanent gate stack. For example, in a specific such embodiment, ananneal of at least a portion of the permanent gate structures, e.g.,after a gate dielectric layer is formed, is performed at a temperaturegreater than approximately 600 degrees Celsius.

Referring again to FIG. 3A, the arrangement of semiconductor structureor device 300 places the gate contact over isolation regions. Such anarrangement may be viewed as inefficient use of layout space. In anotherembodiment, however, a semiconductor device has contact structures thatcontact portions of a gate electrode formed over an active region. Ingeneral, prior to (e.g., in addition to) forming a gate contactstructure (such as a via) over an active portion of a gate and in a samelayer as a trench contact via, one or more embodiments of the presentinvention include first using a gate aligned trench contact process.Such a process may be implemented to form trench contact structures forsemiconductor structure fabrication, e.g., for integrated circuitfabrication. In an embodiment, a trench contact pattern is formed asaligned to an existing gate pattern. By contrast, conventionalapproaches typically involve an additional lithography process withtight registration of a lithographic contact pattern to an existing gatepattern in combination with selective contact etches. For example, aconventional process may include patterning of a poly (gate) grid withseparate patterning of contact features.

It is to be understood that not all aspects of the processes describedabove need be practiced to fall within the spirit and scope ofembodiments of the present invention. For example, in one embodiment,dummy gates need not ever be formed prior to fabricating gate contactsover active portions of the gate stacks. The gate stacks described abovemay actually be permanent gate stacks as initially formed. Also, theprocesses described herein may be used to fabricate one or a pluralityof semiconductor devices. The semiconductor devices may be transistorsor like devices. For example, in an embodiment, the semiconductordevices are a metal-oxide semiconductor field effect transistors (MOS)transistors for logic or memory, or are bipolar transistors. Also, in anembodiment, the semiconductor devices have a three-dimensionalarchitecture, such as a fin-FET device, a trigate device, or anindependently accessed double gate device. One or more embodiments maybe particularly useful for devices included in a system-on-chip (SoC)product. Additionally, it is to be understood that the processing schemedescribed in association with FIGS. 2A-2F could also be applicable toplanar device fabrication.

Overall, embodiments described herein provide approaches to fabricatedifferent workfunctions for different devices. One or more embodimentsenhances the ability to target the performance of each deviceindependently without the extra cost of additional mask operations.

FIG. 4 illustrates a computing device 400 in accordance with oneimplementation of the invention. The computing device 400 houses a board402. The board 402 may include a number of components, including but notlimited to a processor 404 and at least one communication chip 406. Theprocessor 404 is physically and electrically coupled to the board 402.In some implementations the at least one communication chip 406 is alsophysically and electrically coupled to the board 402. In furtherimplementations, the communication chip 406 is part of the processor404.

Depending on its applications, computing device 400 may include othercomponents that may or may not be physically and electrically coupled tothe board 402. These other components include, but are not limited to,volatile memory (e.g., DRAM), non-volatile memory (e.g., ROM), flashmemory, a graphics processor, a digital signal processor, a cryptoprocessor, a chipset, an antenna, a display, a touchscreen display, atouchscreen controller, a battery, an audio codec, a video codec, apower amplifier, a global positioning system (GPS) device, a compass, anaccelerometer, a gyroscope, a speaker, a camera, and a mass storagedevice (such as hard disk drive, compact disk (CD), digital versatiledisk (DVD), and so forth).

The communication chip 406 enables wireless communications for thetransfer of data to and from the computing device 400. The term“wireless” and its derivatives may be used to describe circuits,devices, systems, methods, techniques, communications channels, etc.,that may communicate data through the use of modulated electromagneticradiation through a non-solid medium. The term does not imply that theassociated devices do not contain any wires, although in someembodiments they might not. The communication chip 406 may implement anyof a number of wireless standards or protocols, including but notlimited to Wi-Fi (IEEE 802.11 family), WiMAX (IEEE 802.16 family), IEEE802.20, long term evolution (LTE), Ev-DO, HSPA+, HSDPA+, HSUPA+, EDGE,GSM, GPRS, CDMA, TDMA, DECT, Bluetooth, derivatives thereof, as well asany other wireless protocols that are designated as 3G, 4G, 5G, andbeyond. The computing device 400 may include a plurality ofcommunication chips 406. For instance, a first communication chip 406may be dedicated to shorter range wireless communications such as Wi-Fiand Bluetooth and a second communication chip 406 may be dedicated tolonger range wireless communications such as GPS, EDGE, GPRS, CDMA,WiMAX, LTE, Ev-DO, and others.

The processor 404 of the computing device 400 includes an integratedcircuit die packaged within the processor 404. In some implementationsof embodiments of the invention, the integrated circuit die of theprocessor includes one or more devices, such as MOS-FET transistorsbuilt in accordance with implementations of the invention. The term“processor” may refer to any device or portion of a device thatprocesses electronic data from registers and/or memory to transform thatelectronic data into other electronic data that may be stored inregisters and/or memory.

The communication chip 406 also includes an integrated circuit diepackaged within the communication chip 406. In accordance with anotherimplementation of the invention, the integrated circuit die of thecommunication chip includes one or more devices, such as MOS-FETtransistors built in accordance with implementations of the invention.

In further implementations, another component housed within thecomputing device 400 may contain an integrated circuit die that includesone or more devices, such as MOS-FET transistors built in accordancewith implementations of embodiments of the invention.

In various embodiments, the computing device 400 may be a laptop, anetbook, a notebook, an ultrabook, a smartphone, a tablet, a personaldigital assistant (PDA), an ultra mobile PC, a mobile phone, a desktopcomputer, a server, a printer, a scanner, a monitor, a set-top box, anentertainment control unit, a digital camera, a portable music player,or a digital video recorder. In further implementations, the computingdevice 400 may be any other electronic device that processes data.

Thus, embodiments of the present invention include non-planar I/O andlogic semiconductor devices having different workfunctions on commonsubstrates and methods of fabricating non-planar I/O and logicsemiconductor devices having different workfunctions on commonsubstrates.

In an embodiment, a semiconductor structure includes a firstsemiconductor device disposed above a substrate. The first semiconductordevice has a conductivity type and includes a gate electrode having afirst workfunction. The semiconductor structure also includes a secondsemiconductor device disposed above the substrate. The secondsemiconductor device has the conductivity type and includes a gateelectrode having a second, different, workfunction.

In one embodiment, the first semiconductor device is an I/O transistor,and the second semiconductor device is a logic transistor.

In one embodiment, the gate electrode having the first workfunctionincludes a first workfunction metal layer having a thickness, the gateelectrode having the second workfunction includes a second workfunctionmetal layer having a thickness, and the thickness of the firstworkfunction metal layer is different than the thickness of the secondworkfunction metal layer.

In one embodiment, the gate electrode having the first workfunctionincludes a first workfunction metal layer having a total materialcomposition, the gate electrode having the second workfunction includesa second workfunction metal layer having a total material composition,and the total material composition of the first workfunction metal layeris different than the total material composition of the secondworkfunction metal layer.

In one embodiment, the gate electrode having the first workfunctionincludes a first workfunction metal layer having a total materialcomposition and a thickness, the gate electrode having the secondworkfunction includes a second workfunction metal layer having a totalmaterial composition and a thickness, and both the total materialcomposition and the thickness of the first workfunction metal layer aredifferent than the total material composition and the thickness of thesecond workfunction metal layer.

In one embodiment, the conductivity type is N-type.

In one embodiment, the gate electrode having the first workfunctionincludes a first workfunction metal layer having a thickness, the gateelectrode having the second workfunction includes a second workfunctionmetal layer having a thickness. The thickness of the first workfunctionmetal layer is greater than the thickness of the second workfunctionmetal layer, and the first workfunction is closer to mid-gap than thesecond workfunction by an amount approximately in the range of 50-80mVolts.

In one embodiment, the gate electrode of the first semiconductor devicehas a gate length different than a gate length of the gate electrode ofthe second semiconductor device.

In one embodiment, both the first and second semiconductor devices arefin-FET or tri-gate devices.

In an embodiment, a system-on-chip (SoC) integrated circuit includes anN-type I/O transistor disposed above a substrate, the N-type I/Otransistor including a gate electrode having a first workfunction and afirst gate length. An N-type logic transistor is disposed above thesubstrate, the N-type logic transistor including a gate electrode havinga second, lower, workfunction and having a second gate length less thanthe first gate length.

In one embodiment, the gate electrode having the first workfunctionincludes a first workfunction metal layer having a thickness, the gateelectrode having the second workfunction includes a second workfunctionmetal layer having a thickness, and the thickness of the firstworkfunction metal layer is greater than the thickness of the secondworkfunction metal layer.

In one embodiment, the gate electrode having the first workfunctionincludes a first workfunction metal layer having a total materialcomposition, the gate electrode having the second workfunction includesa second workfunction metal layer having a total material composition,and the total material composition of the first workfunction metal layeris different than the total material composition of the secondworkfunction metal layer.

In one embodiment, the gate electrode having the first workfunctionincludes a first workfunction metal layer having a total materialcomposition and a thickness, the gate electrode having the secondworkfunction includes a second workfunction metal layer having a totalmaterial composition and a thickness, and both the total materialcomposition and the thickness of the first workfunction metal layer aredifferent than the total material composition and the thickness of thesecond workfunction metal layer.

In one embodiment, the first workfunction is closer to mid-gap than thesecond workfunction by an amount approximately in the range of 50-80mVolts.

In one embodiment, both the first and second semiconductor devices arefin-FET or tri-gate devices.

In an embodiment, a method of fabricating a semiconductor structureinvolves forming a first semiconductor fin and a second semiconductorfin above a substrate. The method also involves forming a firstplurality of gate lines having a first pitch over the firstsemiconductor fin and forming a second plurality of gate lines having asecond, narrower, pitch over the second semiconductor fin, both of thefirst and second pluralities of gate lines including a firstworkfunction metal layer of a conductivity type. The method alsoinvolves replacing the first workfunction metal layer of theconductivity type with a second workfunction metal layer of theconductivity type in the first plurality of gate lines but not in thesecond plurality of gate lines.

In one embodiment, forming the first plurality of gate lines and thesecond plurality of gate lines involves using a replacement gatetechnique.

In one embodiment, replacing the first workfunction metal layer of theconductivity type with the second workfunction metal layer of theconductivity type involves masking a portion of the first workfunctionmetal layer of the conductivity type in the second plurality of gatelines, but not in the first plurality of gate lines.

In one embodiment, masking the portion of the first workfunction metallayer of the conductivity type in the second plurality of gate linesinvolves forming and etching a carbon hardmask. The etch rate of thecarbon hardmask in the second plurality of gate lines is slower than theetch rate of the carbon hardmask in the first plurality of gate lines.

In one embodiment, replacing the first workfunction metal layer of theconductivity type with the second workfunction metal layer of theconductivity type involves etching the first workfunction metal layer ofthe conductivity type and forming the second workfunction metal layer ofthe conductivity type with a thickness greater than a thickness of thefirst workfunction metal layer of the conductivity type.

In one embodiment, the method further involves forming an I/O transistorfrom the first semiconductor fin and the first plurality of gate lines.The method also involves forming a logic transistor from the secondsemiconductor fin and the second plurality of gate lines.

In one embodiment, forming the I/O transistor involves forming an N-typeI/O transistor, and forming the logic transistor involves forming anN-type logic transistor.

1. An integrated circuit structure, comprising: a first N-type fin-FETdevice having a first fin, the first N-type fin-FET device comprising afirst gate electrode having a first layer having a composition, thefirst layer having a first thickness; and a second N-type fin-FET devicehaving a second fin, the second N-type fin-FET device comprising asecond gate electrode having a second layer having the composition, thesecond layer having a second thickness greater than the first thickness,wherein the second gate electrode of the second N-type fin-FET devicehas a gate length greater than a gate length of the first gate electrodeof the first N-type fin-FET device.
 2. The integrated circuit structureof claim 1, wherein the first N-type fin-FET device is a logictransistor, and the second N-type fin-FET device is an I/O transistor.3. The integrated circuit structure of claim 1, further comprising: afirst gate dielectric between the first fin and the first gateelectrode; and a second gate dielectric between the second fin and thesecond gate electrode.
 4. The integrated circuit structure of claim 1,wherein the first and second gate dielectrics comprise hafnium andoxygen.
 5. The integrated circuit structure of claim 1, wherein thefirst and second layers comprise aluminum.
 6. The integrated circuitstructure of claim 1, wherein the first and second layers comprisetitanium.
 7. The integrated circuit structure of claim 1, wherein thefirst and second layers comprise a metal carbide.
 8. An integratedcircuit structure, comprising: a first P-type fin-FET device having afirst fin, the first P-type fin-FET device comprising a first gateelectrode having a first layer having a composition, the first layerhaving a first thickness; and a second P-type fin-FET device having asecond fin, the second P-type fin-FET device comprising a second gateelectrode having a second layer having the composition, the second layerhaving a second thickness greater than the first thickness, wherein thesecond gate electrode of the second P-type fin-FET device has a gatelength greater than a gate length of the first gate electrode of thefirst P-type fin-FET device.
 9. The integrated circuit structure ofclaim 8, wherein the first P-type fin-FET device is a logic transistor,and the second P-type fin-FET device is an I/O transistor.
 10. Theintegrated circuit structure of claim 8, further comprising: a firstgate dielectric between the first fin and the first gate electrode; anda second gate dielectric between the second fin and the second gateelectrode.
 11. The integrated circuit structure of claim 8, wherein thefirst and second gate dielectrics comprise hafnium and oxygen.
 12. Theintegrated circuit structure of claim 8, wherein the first and secondlayers comprise aluminum.
 13. The integrated circuit structure of claim8, wherein the first and second layers comprise titanium.
 14. Theintegrated circuit structure of claim 8, wherein the first and secondlayers comprise a metal carbide.
 15. A computing device, comprising: aboard; and a component coupled to the board, the component including anintegrated circuit structure, comprising: a first N-type fin-FET devicehaving a first fin, the first N-type fin-FET device comprising a firstgate electrode having a first layer having a composition, the firstlayer having a first thickness; and a second N-type fin-FET devicehaving a second fin, the second N-type fin-FET device comprising asecond gate electrode having a second layer having the composition, thesecond layer having a second thickness greater than the first thickness,wherein the second gate electrode of the second N-type fin-FET devicehas a gate length greater than a gate length of the first gate electrodeof the first N-type fin-FET device.
 16. The computing device of claim15, further comprising: a memory coupled to the board.
 17. The computingdevice of claim 15, further comprising: a communication chip coupled tothe board.
 18. The computing device of claim 15, further comprising: acamera coupled to the board.
 19. The computing device of claim 15,further comprising: a battery coupled to the board.
 20. The computingdevice of claim 15, wherein the component is selected from the groupconsisting of a processor, a communications chip, and a digital signalprocessor.